1. Field of the Invention
The present invention relates to an ink suitable for ink jet, an ink cartridge using the ink and an ink jet recording method.
2. Description of the Related Art
The ink jet recording method enables recording on various type of recording medium. As attempts for more satisfactory image recording, various inks suitable for particular purposes have been proposed, such as inks suitable for recording images of photographic image quality on the recording medium such as glossy paper and inks suitable for recording documents on the recording medium such as plain paper. Recently, the ink jet recording method has been utilized for printing business texts including characters, tables, figures and the like, by using a recording medium such as plain paper; the frequency of use of the ink jet recording method in such uses has been dramatically increased. In such uses, from the viewpoint of economic efficiency, further improvement of color developability of the obtained images even with small application amounts of ink has been demanded.
Various investigations have also hitherto been made for the purpose of enhancing the color developability of the obtained images even with small application amounts of ink. For example, there is a proposal of an ink including a self-dispersible pigment capable of being dispersed in the ink without using a dispersant such as a water-soluble resin and a specific salt (see Japanese Patent Application Laid-Open No. 2001-081378). There is also a proposal of an ink including a self-dispersible pigment to the surface of the particle of which a functional group highly reactive with calcium is bonded (see Japanese Patent Application Laid-Open No. 2009-515007). Moreover, there is a proposal of an ink including a self-dispersible pigment, a poor medium and a good medium (see Japanese Patent Application Laid-Open No. 2006-045514). According to the statement in Japanese Patent Application Laid-Open No. 2006-045514, the dots formed by the ink are spread while the pigment is being aggregated, by using a poor solvent relatively high in permeability, and thus high color developability is obtained even when the ink droplets are small.